(1) Field of the Invention
This invention relates to polyvinyl alcoholbased compositions and more particularly to adhesives containing polyvinyl alcohol or ethylene/vinyl alcohol copolymer, a crystalline solvent for the polymer and a viscosity reducing diluent.
(2) Description of the Prior Art
Japanese Patent Publication No. 12851/72 describes the preparation of shaped articles of polyvinyl alcohol. The process involves the preparation of an up to 20 percent by weight aqueous polyvinyl alcohol solution and the addition of 5-55 percent by weight, based on the weight of the aqueous solution, of urea thereto. Thereafter, uniform stress is applied to the aqueous solution by mechanical stirring. The polyvinyl alcohol/water/urea blend employed in this process contains 0.1 to 19 percent polyvinyl alcohol, 55 to 95 percent water and 5 to 36 percent urea, all based on the total weight of the solution. The shaped articles prepared by this process are disclosed to be useful as highly tenacious nonwoven fabrics, as fluff for mattress wadding or as filaments obtained by splitting the shaped article. There is no disclosure of the suitability of either the aqueous solutions or the shaped articles as adhesives.
U.S. Pat. No. 3,313,637 discloses models which may be separated readily from their molds. The models consist of a major portion by weight of a finely divided crystalline material (such as urea), a minor portion by weight of a finely divided organic material (such as polyvinyl alcohol) and a liquid solvent for the crystalline material (such as water). Example 1 discloses the use of a composition comprising 85 percent urea, 10 percent polyvinyl alcohol and 5 percent water. There is no disclosure whatsoever of adhesive use generally or as a hot melt adhesive specifically; on the contrary, it is emphasized that the model after pressing can be readily extracted from the matrix in which it was formed.